1894 J . Org. Chem., Vol. 44, No. 11,1979
a methanolic solution of diazomethane. The reaction mixture was chromatographed on a column of silica gel. Elution with hexane-ethyl acetate (4:6) provided 4c (169 mg) and 4-(methylthio)-3-(2’,3’,5’tri-0-acetyl-D-ribofuranosy1)pyridine [5c (11mg, 59611 as an anomeric mixture. 5c: MS mle 384 [(Mt I)+-],323 [(M- 60)+.]; NMR6 8.90 (d, 1,H-6),8.47 (s, 1,H-2),6.96 (d, 1,H-5), 5.50-5.07 (m, 3, H-1’, H-2’, and H-3’), 4.40-4.10 (m, 3, H-4’ and 2 X H-5’),2.46 (s, 3, CH3S),2.12, 2.08, and 2.05 (3 X ) (s, 3, CHsCO). Treatment of compound 5c (24 mg) with NaOCH3 in methanol followed by neutralization with Amberlite IR 120 (H+)gave an anomeric mixture oi pseudonucleosides which after reaction with 2,2dimethoxypropane gave the corresponding mixture of acetonide derivatives 4d. Purification of the /3 isomer was accomplished by silica gel preparative TLC (CHC13-MeOH, 9:l) to give 3-(2’,3’-0-isopropylidene-~-D-ribofuranosyl)-4-(methylthio)pyridine [P-5d (12 mg)] as an amorphous solid. 8-5d (C14H19N04S):M+- found 297.1030; UV , , ,A 264 nm ( t 11 000): NMR 6 8.50 (s 1,H-2), 8.39 (d, J = 5.5 Hz, 1, H-6), 7.07 (d, J =: 5.5 Hz, 1, H-5),5.08(d,J = 4 Hz, 1,H-l’),4.78 (m, 2, H-2’and H-39, 4.13 (m,1, H-49, 3.96-3.73 (m, 2, 2 X H-59, 2.45 (s, 3. CH$), 1.63 arid 1.36 ( 2 X ) (s, 3, CH?).
Acknowledgment. We would like t o thank Mr. G. Henry for his efficient technical assistance and t h e DBl6gation GBn6rale d e la Recherche Scientifique e t Technique for support, We are also thankful t o Dr. J. Polonsky for her interest in this work. Registry No.-1 (R = CHs), 18438-38-5; la, 51290-79-0; lb, 2637-34-5; IC, 69493-87-4;2a, 69493-88-5;a-2d, 69493-89-5;@-2d, 69502-45-0;3a, 69493-90 9; a-3d, 69493-91-0;@-3d,69493-92-1;4 (R = CHs), 22581-72-2;4a, 51290-78-9;4b, 4556-23-4;a-Gc, 69493-93-2; @-4c,69493-94-3 n-4d, 69493-95-4;@-4d,69493-96-5;5a, 69493-97-6; n - k ,69493-98-7;/3-5c,69493-99-8;@-5d,69494-00-4;6 (R = ribosyl), 54606-57-4; 6c, 69494-01-5; 6d, 69494-02-6; 1,2,3,5-tetra-O-acetylD-ribofuranose. ‘l8708-32-9.
References and Notes R. J. Suhadolnik, “Nucleoside Antibiotics”, Wiley-lnterscience, New York. 1970. S. Hanessian and A. G. Pernet, Adv. Carbohydr. Chem. Biochem., 33, 111 (1976). R. W. Brockman, S.C. Shaddix, M. Williams, J. A. Nelson, L. M. Rose, and F. M. Schabel. Jr., Ann. N.Y. Acad. Sci., 255,501 (1975), and references cited therein. J.-L. Fourrey, G. Henry, and P. Jouin, J. Am. Chem. SOC., 99, 6753 (1977). R. A. Jones and A. R. Katritzky, J. Chem. SOC.,3610 (1958). D. A. Shuman. A. Bloch, R. K. Robins, and M. J. Robins, J. Med. Chem., 12, 653 (1969). H. Pischel, P. Nuhn, E.Liedmann, and G. Wagner, J. Prakt. Chem. 316,615 (1974). Although ribose numbering is formally incorrect, we use it for convenience. For a recent discussion and pertinent references on the application of ’H NMR approaches for assigning nucleoside configration, see M. J. Robins and M. McCos, J. Am. Chem. SOC.,99, 4654 (1977). J. L. Imbach, Ann. N.Y. Acad. Sci., 255, 177 (1975). J. D. Stevens and H. G. Fletcher, Jr., J. Org. Chem., 33, 1799 (1968); L. B. Townsend, Synth. Proced. Nucleic Acid Chem. 7973,2, 333 (1973). M. McCoss, kl. J. Robins, B. Rayner, and J. L. Imbach, Carbohydr. Res., 59, 575 (1977). The difference’ in the stereoselective course for the preparation of 2c and 4c might be e.rplained by considering that 4-(alky1thio)pyridines are more basic than 2-(alkylthio)pyridines( ~ P K ~ Consequently, ) . ~ under the reaction conditions the pyridinium species derived from 4c might undergo a nucleophilic substitution involving 4mercaptopyridine (4b) to give the corresponding a-thionucleoside. In support of this view we have observed the formation of a minor amount of 2c when we treated an anomeric mixture of 4c with 2-niercapotpyridine (2b) in the presence of BF3:Et20in dichloroethane. G. Szekeres 2nd T. J. Pardos, J. Med. Chem., 15, 1333 (1972).
Preparation of a-Substituted @-AlanineDerivatives from 5-Substituted Uracils and Dihydrouracils Robert F Dietrich,’ Tadamitsu Sakurai, and George L Kenyon*j D e p a r t m e n t of Pharmaceutical C h e m i s t r ) , [.nit ersit3 of Caiifornia, S u n Franczwo, California 94143
ReteiLed NoLember 14, 1978
In the course of synthesizing new cyclic analogues of creatine t o examine t h e substrate specificity of t h e enzyme cre-
Notes Scheme I
H, Rd/alumina
H 3, R , = R, = H 4, R , = CH,;
R,
=
CH,Ph
H
HC1
5 , R , = R, = H
6,R , = CH,; R, = H
1, R , 2, R ,
= =
R, = H CH,; R,
=
H
atine kinase, we needed reasonable quantities of both 2,3diaminopropanoic acid ( I ) and Z-(methylamino)-3-aminopropanoic acid (2).Compound 1 is available commercially a t high cost and can be prepared as t h e dihydrobromide from 2,3-dibromopropanoic acid and ammonia, but the yield is only 40-50% and high temperatures and pressure are required.3 2-(Methylamino)-3-aminopropanoic acid (2) was first reported4 as one of the hydrolysis products of deoxytheobromine (3,7-dimethyl-2-oxo-1,6-dihydropurine).5 This synthetic procedure, which first requires the reduction of theobromine to d e o ~ y t h e o b r o m i n e suffers ,~ from low yields and, in our hands, poor reproducibility. Martin e t aL6 also report a synthesis of 2, in this case from t h e condensation of diethyl (N-methyl-A’-acety1amino)malm a t e s a n d N-(bromomethyl)phthalimides followed by acid-catalyzed hydrolysis of the condensation product. A 30% yield was reported for these final two steps.6 An alternative method for the synthesis of compounds 1and 2 is presented in Scheme I. Compound 3, 5-aminouracil, is commercially available, and is easily prepared in 4, 5-(N-benzyl-N-methylamino)uracilg high yield from commercially available 5-bromouracil. T h e hydrogenation steps are nearly quantitative for 3 and 4. T h e acid-catalyzed hydrolyses of 5 a n d 6 each give 1 equiv of ammonium chloride as a coproduct along with t h e dihydrochloride of the corresponding diamino acid. T h e two products are easily separated by means of ion exchange chromatography on a strongly basic anion exchange resin. T h e amino acid and chloride ion bind tightly t o t h e column, and the ammonia is eluted with water. T h e amino acid can then be removed from t h e column by elution with an acidic solution, e.g., 1.0 N HC1 or 1.0 N HC02H. T h e overall method should be directly applicable to the preparation of a variety of 2-(alkylamino)-3-aminopropanoic acids from other 5-substituted aminouracils, which in turn are easily prepared from 5-bromouracil and t h e appropriate amine.g Also, any 5-substituted uracil derivative in which t h e 5-substituent is stable to the hydrogenation and acid-catalyzed hydrolysis conditions potentially could be converted to t h e corresponding a-substituted @-alaninederivative. Some @-substituted@-alaninederivatives have been prepared from their corresponding 6-substituted dihydrouracils in good yields using similar methods to those we describe here, although convenient starting materials are not commercially available and not all of the 6-substituted dihydrouracils examined gave the expected @-alanine derivatives.’O We have extended this procedure to obtain reasonably high
0022-326317911944-1894$01.00/0C 1979 American Chemical Society
J . Org. Chem., Vol. 44, No. 11, 1979
Notes S c h e m e I1
0
H-
8 N HCI 90-h reflux
'NH, C1-
CO,H
k 9,R=H
10,R = CH,
anion exchange
resin
1895
water was removed in vacuo. The product ( 5 ) was purified by recrystallization from ethanol-water to give 9.6 g (97%yield) of colorless crystals, m p 239-241 "C dec. Anal. Calcd for C4H8ClN302: C, 29.02; H, 4.87; C1,21.41; N, 25.38. Found: C, 28.93; H, 4.92; C1, 21.16; N, 25.11. T h e 'H NMR spectrum showed peaks at 6 3.3-4.1 (2 H, multiplet, ABC pattern) and 4.54 (1 H, doublet of doublets, J = 7 and 13 Hz). 2,3-Diaminopropanoic Acid Monohydrochloride (1). 5Amino-5,6-dihydrouracil hydrochloride (5; 6.0 g, 36 mmol) was heated a t reflux for 72 h in 150 mL of 6 N HC1. The aqueous acid was removed at reduced pressure, and the residue was taken up in water several times and concentrated in vacuo to remove residual HCI, leaving the dihydrochloride of 2,3-diaminopropanoic acid and 1 equiv of ammonium chloride. The product was dissolved in 5 mL of water and applied t o a 50-g column of Bio-Rad AG-l-X8, 20-50 mesh, -OH form, anion exchange resin. The column was eluted with water until the effluent was neutral to pH paper. The diamino acid was then eluted with 1 N HC1 as the dihydrochloride salt until the column effluent was no longer ninhydrin-positive. The product, after concentration in vacuo, was dissolved in a minimum amount of warm methanol, and pyridine was added to the solution until the pH rose to a value of about 4. The precipitate was recrystallized from aqueous ethanol to give 4.6 g (90% yield) of 2,3-diaminopropanoic acid monohydrochloride ( l ) , m p 225-226 " C (lit.?*mp 226-227 "C). The proton NMR was identical with that of the commercially available material. 5,6-Dihydro-5-(methylamino)uracilHydrochloride (6). 5(N-Methyl-N-benzy1amino)uracilhydrochloride (4; 4.0 g, 15 mmol) was hydrogenated as in the 3 5 conversion to give a quantitative yield of 5,6-dihydro-5-(methylamino)uracil hydrochloride (6, 2.65 g). A sample was recrystallized for elemental analysis from aqueous ethanol, m p 239-240 "C. Anal. Calcd for CSH10N302Cl: C, 33.44; H, 5.61: N. 23.40. Found: C, 33.15; H , 5.50; N, 23.13. The 'H NMR spectrum showed peaks a t d 2.91 (3 H, singlet) and an ABC pattern at 6 4.53 ( J = 6.5 and 12.5 Hz). 2-(Methylamino)-3-aminopropanoicAcid Monohydrochloride (2). 5,6-Dihydro-5-(methylamino)uracil(6; 2 g, 11.1mmol) was heated at reflux for 72 h in 50 mL of 6 N HC1, after which the aqueous HC1 was removed in vacuo. The crude product was separated from the ammonium chloride and converted to the monohydrochloride as in the 5 1 conversion. The pH of the resulting methanol solution was adjusted to approximately 5 with pyridine, and the white crystalline solid that formed was collected by filtration to give 1.3 g of product 2 (76%yield). A sample was recrystallized from aqueous ethanol for elemental analysis, mp 200-213 "C dec. Anal. Calcd for C4HllN202C1:C, 31.08: H, 7.17: N, 18.12;C1,22.93. Found: C, 31.21; H, 7.17; N. 18.18; C1, 22.88. The 'H NMR spectrum showed peaks at 6 3.85 ( 3 H, singlet) and an ABC pattern at 6 3.4-4.2 with a doublet of doublets centered a t 6 4.0 ( J = 5 and 8.5 Hz).
dR c0,-
+NH~
7,R=H 8, R = CH,
yields (77-87%) of both @-alanine'7) and @-aminoisobutyric acid (8) by the hydrolyses of commercially available dihydrouracil (9) and 5-methyldihydrouracil (IO), respectively, as shown in Scheme 11. Both 7 and 8 had been previously prepared in 56-65% yield by Zilkha et al." by the hydrogenolysis of the corresponding N-benzyl derivatives, which were prepared by the addition of benzylamine t o acrylic acid or methacrylic acid, respectively. A number of other less general methods have been reported for the syntheses of P-alanine12-16 a n d @-aminoisobutyricacid.17-21 E x p e r i m e n t a l Section General. Proton NMR spectra were determined on a Varian A-60A spectrometer in DzO and are reported relative to the internal standard sodium 2,2-dimethyl-2-silapentane-5-sulfonate (DSS).Melting points are uncorrected, and microanalyses were obtained from the Microanalytical Laboratory, Department of Chemistry, University of California, Berkeley, Calif. @-Alanine (7) f r o m Dihydrouracil (9). Dihydrouracil (9; 3.0 g, 26 mmol; Sigma Chemical Co.) was heated at reflux for 90 h in 105 mL of 8 N HC1. The excess HC1 and water were removed in vacuo. After t h e residual solid was washed with acetone several times, the dry product was heated under reflux with stirring in 100 mL of 2-propanol until the lumps disintegrated. The coproduct, NHdCl, was filtered off and washed with 30 mL of hot 2-propanol. The filtrate, on cooling overnight, gave 2.0 g of the crystalline product. By concentrating the filtrate t o 1.0-20 niL and cooling, an additional 0.5 g of the product was obtained (total 2.5 g, 77% yield). On recrystallization from 2propanol, the product, P-alanine hydrochloride, melted a t 122-123 o c (iit.13 121-122 o c ) . /%Alanine hydrochloride (2.0 g, 16 mmol) was dissolved in 3 mL of water and passed through a column packed with weakly basic anion exchange resin (Bio-Rad AG3-X4A, 20-50 mesh, -OH form) containing 20 mL of resin a t the rate of 1-2 mL/min with water as eluent. Ninhydrin-positive fractions were pooled and concentrated to dryness in vacuo to give crystalline, hydrochloride-free p-alanine (7) in 93100% yield. Recrystallization from aqueous ethanol gave analytically pure 7 as white crystals (79-85% recovery), mp 197-198 "C dec (lit.14 197-198 " C dec). &Aminoisobutyric Acid (8) from 5-Methyldihydrouracil (10). 5-Methyldihydrouracil(lO; 4.0 g, 31 mmol; Sigma Chemical Co.) was heated a t reflux in 120 mL of 8 N HC1 for 90 h. The same procedure as described above for the isolation of @-alaninehydrochloride gave crystalline P-aminoisobutyric acid hydrochloride in 80-87% yield. On recrystallization from 2-propanol, the hydrochloride of 8 melted at 127-129 " C . By treating the hydrochloride with weakly basic anion exchange resin as described in the preparation of @-alanine,the hydrochloride-free product was obtained in 9 g l W 0yield. The white crystalline product (lo), which was recrystallized from 95% ethanol-acetone, melted at 176.5-177.5 "C (lit. 18111and 171-172 "CZo);lH NMR 6 1.16 ( 3 H , d , J = 8 Hz). 2.2-3.1 (3 H, m). 5-Amino-5,6-dihydrouracil Hydrochloride (5). 5-Aminouracil (3; 7.7 g, 60 mmol; Aldrich Chemical Co.) was converted to its hydrochloride salt by treatment with 6 N HCI followed by removal of the excess aqueous acid in vacuo. The pale yellow solid was then suspended in 200 mL of water and hydrogenated (45 psi) in the presence of 1 g of 5% rhodium on powdered alumina (Matheson Coleman and Bell). After the theoretical amount of hydrogen had been absorbed (24 h), the catalyst was separated by filtration and the
-
-
Acknowledgments. This work was supported by U S . Public Health Service Grant AM 17323, National Institute of Arthritis, Metabolism and Digestive Diseases. Registry No.-1, 6018-55-9; 2, 69652-324: 3, 69652-31-9; 4, 69686-93-7; 5,69652-33-1;6,69652-34-2; 7,107-95-9; 7 hydrochloride, 6057-90-5:8,144-90-1;8, hydrochloride, 28267-25-6;9, 504-07-4; 10, 696-04-8.
R e f e r e n c e s a n d Notes (1) National Institutes of Health Predoctoral Trainee, 1976-1978 (Training Grant GM 00728 to the Department of Pharmaceutical Chemistry).Present ad-
dress: Department of Chemistry, Pennsylvania State University, University Park, Pa. 16802. (2) Recipient of a Research Career Development Award, AM 00014, from the National Institute of Arthritis, Metabolism and Digestive Diseases, 1975-1980. (3) K. Poduska, J. Rudinger, and F. Sorm, Collect. Czech. Chem. Conimun.,
20, 1174 (1955). (4) J. Tafel and E. P. Frankland, Chem. Ber., 42,3138 (1909). (5) J. Tafel, Chem. Ber., 32,3194(1899). (6) P. K.Martin, H. R. Mathews, H. Rapoport, and G. Thyagarajan. J. Org. Chem., 33,3758 (1968). (7) F. C. Uhle and L. S.Harris, J. Am. Chem. Soc., 78,381 (1956). (8)0. Mancera and 0. Wemberger, J. Org. Chem., 15, 1253 (1950). (9) A. P. Phillips, J. Am. Chem. SOC.,73, 1061 (1951). (10) L. Birkofer and I. Storch, Chem. Ber., 86,529 (1953). (11) A. Zilkha, E. S. Rachman, and J. Rivlin. J. Org. Chem., 26,376 (1961). (12) H. T. Clarke and L. D. Behr, "Organic Syntheses". Collect. Vol. 2, Wiley, New York, 1943, p 19, and references cited therein. (13) S. R. BUC, J. H. Ford, and E. C. Wise, J. Am. Chem. Soc., 67, 92
1896 J. Org. Chem., Vol. 44, No. 11, 2979 (1945). (14) J. H. Ford, "Organic Syntheses", Collect. Vol. 3,Wiley, New 'fork, 1955, p 34, and references cited therein. (15) F. Poppelsdorf and R. C. Lemon, J. Org. Chem., 26, 262 (1961). (16) R. M. Fink, K. Fink, and R. B. Henderson, J. Bioi. Chem., 201, 349 (1953). (17) M. A. Pollack, J. Am. Chem. SOC., 65, 1335 (1943). (18) T. L. Gresham and F. W. Shaver, U.S. Patent 2 525 794, 1950; Chem.
Notes Abstr., 45, P 2971f.(1951). (19) K. Balenovic and I. Jambresic, Chem. Ind. (London). 1673 (1955). (20) S. Sato, Ma. Takesada, and H. Wakamatsu, Nippon Kagaku Zasshi, 90, 579 (1969); Chem. Abstr., 71, 49178u (1969). (21) B. W. lofee, V. A. Isidorov,andB. V. Stolyarow. Dokl. Akad. Nauk. SSSR. 197, 91 (1971); Chem. Abstr., 75, 209558 (1971). (22) T. J. McCord, J. M. Ravel, C. G. Skinner, and W. Shive, J. Am. Chem. SOC., 79, 5693 (1957).
